1. Technical Field
The present invention relates to an electronic timepiece that receives signals transmitted from GPS satellites or other positioning information satellites and displays information.
2. Related Art
The Global Positioning System (GPS) uses GPS satellites (positioning information satellites) that orbit the Earth on known orbits and enables a GPS receiver (GPS device) to determine its own location from these GPS signals. Each GPS satellite carries an atomic clock, and transmits satellite signals that contain time information (GPS time information) expressing the time (GPS time) that is kept by the atomic clock. The GPS time is the same on all GPS satellites, and UTC (Coordinated Universal Time) is determined by correcting the GPS time with the UTC offset (currently +15 seconds), which is the difference between GPS time and UTC. UTC can therefore be determined by receiving a satellite signal from a GPS satellite and acquiring the GPS time, and then correcting the GPS time based on the UTC offset.
Japanese Unexamined Patent Appl. Pub. JP-A-H 10-197662 teaches an electronic timepiece (“GPS timepiece” below) that receives satellite signals from GPS satellites and obtains the current time. A stacked construction that has the antenna for receiving satellite signals and the dial for displaying the time on the surface one above the other is desirable as a means of reducing the size of the GPS timepiece, but if the antenna is disposed on the face side of the dial, the part of the dial where the antenna is located cannot be used for a functional display (such as displaying the date). JP-A-H 10-197662 therefore teaches a configuration having the antenna located behind the dial.
With the development of efficient, low power consumption GPS reception circuits, solar power can now be used to meet the power supply needs of an electronic timepiece that obtains the current time by receiving and processing satellite signals from GPS satellites. More specifically, GPS timepieces that have a solar cell for converting light energy to electrical energy to power the timepiece are now possible. Depending on the location of the solar cell, however, antenna sensitivity can be significantly degraded. For example, if a solar cell is added to the timepiece taught in JP-A-H 10-197662, the solar cell will naturally be added between the dial and the antenna, covering the antenna. However, solar cells contain metal materials, and microwaves such as those that carry satellite signals are easily affected by metal. Antenna sensitivity therefore drops dramatically if the antenna is covered by the solar cell.